9 x 5 x 3 inch loaf pan. Stir the topping ingredients together in a small bowl until smooth. Set aside. In a medium size bowl, stir the sugar, milk, butter and egg together until smooth. In another bowl, toss the flour with the baking powder and salt. Stir this into the wet ingredients, and then fold in the blueberries and lemon zest.

Transfer the batter to the prepared loaf pan, and sprinkle with the topping. Bake until the topping is deep golden and has formed a thick crust, 50 minutes. Cool in the pan for 5 minutes, then transfer the bread to a wire rack to continue cooling.